Setting large contiguous blocks of values is not a common use case. In finite elements the values are not contiguous.
> On Apr 20, 2018, at 3:45 PM, Zhang, Junchao <jczh...@mcs.anl.gov> wrote: > > I agree the extra overhead can be small, but users are forced to write a loop > where one single line gives the best. > > --Junchao Zhang > > On Fri, Apr 20, 2018 at 3:36 PM, Smith, Barry F. <bsm...@mcs.anl.gov> wrote: > > When setting values into matrices and vectors we consider the "extra" > overhead of needing to pass in the indices for all the values (instead of > being able to set an arbitrary block of values without using indices for each > one) to be a minimal overhead that we can live with. > > Barry > > > > On Apr 20, 2018, at 3:33 PM, Junchao Zhang <jczh...@mcs.anl.gov> wrote: > > > > > > On Fri, Apr 20, 2018 at 3:18 PM, Matthew Knepley <knep...@gmail.com> wrote: > > On Fri, Apr 20, 2018 at 4:10 PM, Junchao Zhang <jczh...@mcs.anl.gov> wrote: > > To pad a vector, i.e., copy a vector to a new one, I have to call > > VecSetValue(newb,1,&idx,...) for each element. But to be efficient, what I > > really needs is to set a block of values in one call. It looks PETSc does > > not have a routine for that(?). I looked at VecSetValuesBlocked, but it > > looks it is not for that purpose. > > Should we have something like VecSetValuesBlock(Vec v,PetscInt i,PetscInt > > cnt,PetscScalar *value, InsertMode mode) to set cnt values starting at > > index i? > > > > Use VecGetArray(). > > Did you mean VecGetArray b and newb, do a memcpy from b to new and then > > restore them? If yes, it does not work since some of the values I want to > > set might be remote. > > E.g, I have 4 processors. b's size is 181 and is distributed as 46, > > 45,45,45, newb is distributed as 48,45,45,45 to match a matrix of block > > size 3. > > > > > > Matt > > > > --Junchao Zhang > > > > > > > > -- > > What most experimenters take for granted before they begin their > > experiments is infinitely more interesting than any results to which their > > experiments lead. > > -- Norbert Wiener > > > > https://www.cse.buffalo.edu/~knepley/ > > > >
